Presently, radar for chasing or searching targets has been applied extensively. Technologies aiming at enhancing the accuracy of radar have been being provided in the relevant fields so as to increase the accuracy of tracking targets and reduce errors. Normally, radar can be classified into pulsed radar and continuous-wave radar which can further be classified into FMCW radar and Doppler radar.
It is known that the scanning wave of FMCW radar belongs to the low frequency type, and the FMCW radar adopts the low power and has low transmitting peak power so as to avoid danger caused by microwave radiation. Although FMCW dealing with one-time scanning radar-echo has a simple signal processing procedure, it has defects on detecting range against small target: The transmitting scanning time (Ts) of FMCW has to be prolonged to enhance the received SNR; and a MTI (moving target indication) filter is adopted in surroundings with clutter so as to filter the clutter caused by stable objects so as to improve the detection to moving targets; however, if the scanning time is too long, the PRF (pulse repetition frequency) is low and then the doppler clear region of MTI band-pass filter becomes so narrow that the enfoldment of Doppler becomes serious and the target can be filtered together with the clutter by the MTI when the speed of target is a little higher. So, the low PRF (about under 200 Hz) fits detection to low-speed targets and cannot be suitable for high-speed targets. The higher PRF (about 2 KHz) should be adopted to detect high-speed targets. But the high PRF also has its limits. When the PRF is high the Ts is short and the SNR of single scanning is deficient. And the multi-scanning has to be used to improve SNR. The fast fourier transform (FFT) integration is adopted to increase homology gain, which is named as FMCW Doppler processing, and the range against the target and the target speed can be acquired simultaneously. Although the high frequency scanning wave can be used to detect high-speed target, the low speed target can be easily filtered by MTI and the targets with speed differences cannot be detected at the same time.
With the shortage and imperfectness of existing technology, the detection to small targets becomes the trend of detecting radar. The capacity of detecting small targets should be fulfilled under extreme environment and atrocious weather. For the land radar, the sub clutter visibility is an important parameter. For the maritime radar, the compensation for the motion of the movable radar platform must be regarded. For the above reasons, the safety-protection radar faces the challenge of realizing the detection to small targets even in the environment with strong and complex clutter. So, the safety-protection radar not only should have perfect receiving sensitivity but also should have excellent capacity of distinguishing targets and clutter.
The detection to slow small targets by the low-power FMCW radar usually faces the following challenges: the radar cross-section (RCS) of small targets is less than and 1 m2 and is even 0.1 m2 and then the range detection becomes a challenge of low-power radars. For the running environment, whether on land or on the sea, the strength of background clutter is always above the RCS of small targets, and the detection to low-speed small target is so difficult that how to improve the sub clutter visibility of radars under the impact of clutter becomes the other challenge.
The invention discloses the signal processing apparatus of a CW-radar sensing system, being able to enhance range resolution rate, increase SNR, enlarge the detection range, obtain the target speed directly and raise the detection rate for the targets with a wide speed scope, so as to defeat the weakness of existing arts.